A multiplexer has been developed for use with an 8 digit 7 segment display.
Display modules are Kingbright CA56-12SYKWA or CA56-12SURKWA or similar.
Each is a 4 digit display with 4 outputs, one to activate each digit and 8 outputs one to activate each segment ('a' to 'g' plus the colon).
A multiplexer is required since without it every digit would display the same pattern.
The operation of the multiplexer is described in the .PDF attachment “Switch_matrix_operation”.
Circuit details are given in Eagle and .BMP fils “switch matrix circuit”.
The following four C modules are included:
To display integers from 0 to 99999999
To illuminate individual segments
To vary the display intensity
To drive digits singly in the absence of the multiplexer as an aide to fault finding on the pcb.
Note: Display of the colon/decimal point has not been implemented.
All C code is contained in the zip file “Driving the display”